1. Field of the Invention
The present invention generally relates to a heart valve apparatus and method of making the heart valve apparatus. More particularly, the present invention relates to an improved heart valve prosthesis of natural tissue cardiac valves that have been properly fixed in a solution and that may be mounted to an appropriate stent structure prior to implantation into the recipient.
2. Background of the Invention
It is well known to utilize mechanical heart valves, such as the ball check valve, and natural tissue cardiac valves to replace defective aortic and mitral valves in human patients. Referring to the natural tissue heart valves, porcine valves typically are utilized for implantation in humans, because they are very similar to human valves of appropriate size and generally are easy to procure. Prior art teaches the concept of removing an aortic heart valve from a pig, treating it with a glutaraldehyde solution and mounting it into a stent, which may then be implanted into a patient for a heart valve replacement. FIG. 1 illustrates such a prior art heart valve prosthesis, generally indicated as 2, that includes a porcine cardiac valve 4 with a conventional stent construction 6, such as described and disclosed in U.S. Pat. No. 3,983,581 and U.S. Pat. No. 4,035,849 both owned by William W. Angell, the inventor of the present invention.
While anatomically configured, natural tissue heart valve prostheses are well known in the art. Conventional valves often are unable to achieve a completely adequate level of coaptation between the leaflets. In addition, due to the configuration of such heart valve prostheses, there tends to be a significant amount of abrasion between the leaflets of the porcine valve and the conventional stent structures, which generally further decreases the longevity of the valve apparatus. Conventional stent structures are generally formed of a relatively rigid material that tends to be inflexible and difficult to manage by a surgeon during the implant procedure.
Conventional prostheses are typically constructed with a ring of radio-opaque material affixed prosthesis within an implantation flange circumferentially positioned proximal the inflow side of the valve. While the addition of such material, which may be viewed through fluoroscopy, may be beneficial during the post-implantation monitoring of the valve, it generally increases the outer diameter of the entire valve prosthesis and, thus, reduces the inner diameter to outer diameter ratio. U.S. Pat. No. 5,156,621 to Jose A. Navia discloses an unstented heart valve prosthesis that includes a suture ring having a continuous annular cord at the inflow side for implantation and a layer of a textile material covering the exterior of the entire structure. U.S. Pat. No. 4,759,758 to Gabbay discloses a heart valve prosthesis that includes a generally right-circular, cylindrical stent in which a single cusp formed of double over pericardium is mounted. The exterior of the Gabbay prosthesis is completely covered with a biological tissue layer, such as pericardium. A study of this and other such prior art heart valve prostheses readily leads one to the conclusion that such prior art generally fails to completely address the needs of a heart valve prosthesis.